16 ms·

Most news articles I see focus solely on the number of vaccinated people when estimating how far away countries are from herd immunity, which seems odd to me. L

by arbuge 5y ago

Most news articles I see focus solely on the number of vaccinated people when estimating how far away countries are from herd immunity, which seems odd to me. Left out in the discussion seem to be the unvaccinated but already infected. As far as I know, prior infection confers at least some degree of immunity. It may also be the case that those inclined to be skeptical of vaccines were also the ones who exposed themselves to infection most during the pandemic, through disdain for social distancing, mask-wearing, etc. In other words those still unvaccinated in Western countries with easy access to vaccines have a pretty good chance of having been infected by now. Adding those two populations together would seem to indicate that most Western populations are already at herd immunity by this point, which would mean that these surges can be reasonably expected to become smaller and smaller. Unless of course some totally new variant capable of evading all existing vaccines and immunity from prior infection emerges.

billiam 5y ago
I don't know what the point of such conjecture is. Of course we don't know how much immunity comes from infection, and it is quite clear from the spread of delta that we are nowhere near herd immunity in the developed world, even in places like Israel. I had a coronavirus called a cold last year; does that mean I'm immune this year? Unlikely in the long term with COVID. The entire concept of herd immunity may be a mirage: if the (rare) breakthrough infections in vaccinated people like me spread just as much virus as unvaccinated, then there may be a huge potential for incubating new strains among the mRNA-ed that may elude all our current vaccines. And unlike a lot of viruses, the latest variants may be just as lethal as the earlier ones. Usually viruses become more transmissible and less lethal in response to rational behavior in their hosts--but humans are proving we're not rational.
- infamouscow 5y ago
  You're missing the point because the media (and their pharmaceutical advertisers) have framed everything in terms of vaccination, as if the human immune system is incapable of surviving COVID and it's variants. All viruses get less lethal as time goes on, not stronger, despite all the fear porn that has been indoctrinated into the public over the last year and a half.
  - anthonyu 5y ago
    Certain viruses maintained their lethality as time went on. Smallpox was very lethal throughout time. Influenza lethality ebbs throughout history. I don't think we can or should depend on less-lethal, common-cold-like symptoms from Covid-19 at any point.
    - rajin444 5y ago
      Is there a reason we shouldn't expect it to behave like most coroanviruses?
      - cortic 5y ago
        There actually is. The evolutionary selection pressure on most coronaviruses exists throughout its infectious stage. So in order to be more infectious for longer the coronavirus would become less symptomatic and so less serious. But with C19 we are aggressively isolating people with symptoms. This focuses evolutionary selection pressure on the initial infectious stage. In order to be more infectious the virus increases viral load and shedding, causing more serious symptoms; which would be an evolutionary disadvantage, except isolation renders this disadvantage moot. Also natural immunity general focuses on the nucleus of the virus, vaccine immunity is to the spike. So this forces mutations in different proteins, which has different results.
        vimy 5y ago
        Are you saying without lockdowns it would have turned in a regular cold by now?
        deleted 5y ago
        [deleted]
        cortic 5y ago
        Not lock-downs specifically. Testing and isolating, Maybe, but it would have cost many more lives.
- rajin444 5y ago
  > Usually viruses become more transmissible and less lethal in response to rational behavior in their hosts--but humans are proving we're not rational. I was under the impression viruses became less lethal because if they became more, they'd kill off their hosts and be less likely to spread. There's a chance you get some super virus that becomes both more transmissible and lethal, but that is very rare (from what I can see).
  - AbortedLaunch 5y ago
    It depends. It’s hard to model and even think about the selection pressures accurately. West Nile virus showed a marked increase in virulence in corvids recently as did rabbit hemorrhagic disease. And let’s not forget about Mareks disease, where a non-sterilizing vaccine is thought to have contributed to a massive increase in virulence, killing nearly 100% of unvaccinated chickens now vs causing mild disease decades ago.
  - CraigJPerry 5y ago
    Does that not assume that you’re symptomatic at the same time you’re spreading the virus? With covid you appear to be able to spread before you know you have it. Given that, what force would cause the virus to be selected for less lethality? With a different presentation of disease where symptoms and spread occur concurrently then there would be a pressure on the virus selecting for strains that arent so lethal a carrier has no chance to spread. In covid’s case, that pressure doesn’t exist as far as i can see?
  - outworlder 5y ago
    > I was under the impression viruses became less lethal because if they became more, they'd kill off their hosts and be less likely to spread. Only if the lethality is negatively impacting their fitness. If it can spread to another host quickly, who cares if the previous host dies. There's no selective pressure against it. Which is why Delta is scary. Not just because of the higher viral load, but new strains could be more lethal and still not be selected against.
  - deleted 5y ago
    [deleted]
- notJim 5y ago
  > Of course we don't know how much immunity comes from infection Come on, this is silly. We haven't learned nothing over the last year. https://www.nih.gov/news-events/nih-research-matters/lasting-immunity-found-after-recovery-covid-19 https://www.nih.gov/news-events/nih-research-matters/lasting...
  - BeefWellington 5y ago
    This is true, however those studies are for the initial SARS-COV-2 strain and doesn't make any mention of the variants. It's also worth noting that's a study of ~200 people. Given then times we're in it's an excellent sign and possible reason for cautious optimism and I'm sure a larger scale study is much harder to pull off in the midst of the pandemic. That said, I have yet to see a study on the rate of reinfection of any of the variants against people who had already been infected with the initial strain, and how well that is survived, etc.
- throwaway8582 5y ago
  > I had a coronavirus called a cold last year; does that mean I'm immune this year? There are supposedly over 200 different viruses that can cause the common cold (https://www.nih.gov/news-events/nih-research-matters/understanding-common-cold-virus https://www.nih.gov/news-events/nih-research-matters/underst...). So it's quite possible for immunity to any individual strain to last a very long time and still get multiple colds per year. > Usually viruses become more transmissible and less lethal in response to rational behavior in their hosts--but humans are proving we're not rational. Our own "rationality" doesn't matter much, if a virus leaves you bed-ridden or dead, that makes it very hard for you spread it regardless of your choices. The fact that we have so many different viruses which essentially cause more or less the same "common cold" proves that there is very strong evolutionary pressure for a virus to behave this way.
ikawe 5y ago
> and it may also be the case that those who have a tendency to be skeptical of vaccines also were the ones most out and about and exposing themselves during the pandemic, i.e. the ones with the highest chance of being infected. Sure, _maybe_. > [...] would seem to indicate that most Western populations are already at herd imnmunity by this point Given that infections are still rising pretty hard, what indicates to you that we are _at_ this point, and not, say, 6 months out?
basch 5y ago
Not as sensationally reported is that, fatality rate (the proportion of people who die of those who tested positive) appears to be falling slightly, and is at its lowest in 2+ months. https://www.mayoclinic.org/coronavirus-covid-19/map https://www.mayoclinic.org/coronavirus-covid-19/map
- zwily 5y ago
  This would most likely be due to the vaccines, no?
- genericuser314 5y ago
  I think that's because of different vaccine uptake by age cohort. People 65+ have always been most likely to require intervention and they are also the most vaccinated age cohort - ~80% vaccinated in the US. [0] [0]: https://www.mayoclinic.org/coronavirus-covid-19/vaccine-tracker https://www.mayoclinic.org/coronavirus-covid-19/vaccine-trac...
felipellrocha 5y ago
> Left out in the discussion seem to be the unvaccinated but already infected. As far as I know, prior infection confers at least some degree of immunity. We don't know how much, though. There are cases in which vaccine performs better than a natural infection, there are cases in which the vaccine performs worse than natural infection. Without time for a study, it's impossible to know where we lie with Covid.
- gpt5 5y ago
  It's not impossible to estimate for COVID. Re-infections in COVID are exceedingly rare.
  - fortuna86 5y ago
    There's no way of knowing this, considering the amount of asymptomatic cases that are never tested or recorded.
    - deleted 5y ago
      [deleted]
    - nradov 5y ago
      The UK is running human challenge trials to determine that. https://www.reuters.com/world/uk/new-uk-challenge-trial-studies-if-people-can-catch-coronavirus-again-2021-04-18/ https://www.reuters.com/world/uk/new-uk-challenge-trial-stud...
      - fortuna86 5y ago
        It's not if https://www.fox10tv.com/news/coronavirus/getting-covid-19-twice-alabama-health-officials-seeing-more-re-infections/article_21d4404e-effd-11eb-acde-a7bd20cc64d3.html https://www.fox10tv.com/news/coronavirus/getting-covid-19-tw... https://www.nbclosangeles.com/on-air/one-mans-experience-about-getting-covid-twice-even-after-getting-vaccinated/2642507/ https://www.nbclosangeles.com/on-air/one-mans-experience-abo... https://www.sciencemag.org/news/2020/11/more-people-are-getting-covid-19-twice-suggesting-immunity-wanes-quickly-some https://www.sciencemag.org/news/2020/11/more-people-are-gett... But how often and what are the consequences.
bawolff 5y ago
> Adding those two populations together would seem to indicate that most Western populations are already at herd immunity by this point That's assuming that nobody who got covid later got vaccinated (or got it before the vaccine kicked in). That seems like a very unrealistic assumption to me. On the other side, there are probably a lot more cases than are reported. You're right that it almost certainly matters for heard immunity, but i think you need a much more complex model to know how much of an effect it has.
- throw_nbvc1234 5y ago
  https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burden.html https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burd... CDC estimated that 1/4 covid infections had an associated positive test. I did the same kind of napkin math you're referring too for Floridia a few months back and they'd could have been at 80% of the population with some level of immunity. But napkin math probably isn't a good way to run a pandemic response. Just like herd immunity doesn't really matter at an individual level.
  - bawolff 5y ago
    I'm also not sure how much the usa experience applies to other countries. They seem to have not liked lockdowns and masks very much.
stefan_ 5y ago
This is an exposition on Dunning Kruger. What is it going to be, herd immunity or surges? Can't be both.
nostrademons 5y ago
The herd immunity threshold changed with Delta, which I've heard has an R0 of 8-10 (compare 3.5-4.5 for the UK Alpha variant, and about 2.5 for the original strain). Instead of 60% vaccination, you'd need 90%, and will likely overshoot that. It wouldn't surprise me if the UK's cases are now dropping because they reached that threshold, but I doubt the US is there now. Probably Delta will blow through literally all the remaining unvaccinated people and that'll be the last surge, at least unless we get a vaccine-resistant strain.
- deleted 5y ago
  [deleted]
- mensetmanusman 5y ago
  “ Instead of 60% vaccination, you'd need 90%, and will likely overshoot that.” 60% (Vaccinated + Previously Infected)
  - crowbahr 5y ago
    Delta variant can reinfect.
    - arwhatever 5y ago
      It's not a binary consideration, but you have expressed it as such.
- samizdat311 5y ago
  These are very good points. I'd add that herd immunity isn't a clearly defined threshold, either. It's the point at which the effective R in a population is < 1 -- AKA exponential decay. With a circulating virus, depending on how much below 1 you get, exponential decay might take a few months or even a few years to get down to elimination. The current dip in the UK is trending toward the former. But it's further complicated by the fact that levels of immunity in the population will continue to oscillate up and down. (Nevermind that once schools open in September, 20% of the population with relatively sparse vaccination will be mixing in large cohorts). Another factor in herd immunity is vaccine efficacy - which is somewhere between 86% and 95% for the mRNA vaccines (and will continue to change). A herd immunity threshold of 90% presupposes a vaccine with 100% efficacy - when your vaccines are not that effective (not to mention, losing effectiveness over time) it bumps the threshold even higher. Right now, much of the population has some level of "sterilising immunity" from the first round of vaccines and previous infection (i.e. having enough circulating antibodies to potentially block symptomatic infection and transmission). But everything we know about existing respiratory viruses (and indications so far this year) suggest antibodies will wane. Of course, indications are most people will come away with robust cell-based immunity. (Those plucky T-cells and B-cells). But eradication for the UK looks *very* close to impossible given the near-total-abandonment of public health measures recently.
svara 5y ago
Interestingly, you can get multiple-wave dynamics even when very far from population-level herd immunity, and even without taking into account changes in behavior (for example, [1]). That's because of stochasticity in the process due to the fact that (1) most people infect no one, but some people infect many ("overdispersion") and (2) the population is not well mixed. In practice, of course, people respond to news about Covid waves and that contributes to the wave-like dynamics. Furthermore, new variants of the virus will be able to reach people that were "cautious enough" for a previous variant. That alone would also give you wave-like dynamics, basically every new variant would affect increasingly harder to reach people. Anyway, the point is, seeing these waves is super natural and expected and we can't deduce anything about population-level immunity from them without looking really really closely. [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526984/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526984/
hyperpallium2 5y ago
Further, there was an argument way back, that the number infected but symptom-free was much higher than estimated. This would be enhanced by a hypothesised variant, that is more contagious, but less harmful - it would theoretically dominate, because its spread would be unimpeded. I don't know if these arguments have been tested; nor how to test them. Separately, the physical social graph is not uniform, but complex. There can easily be narrower channels that have a lower probability of conducting infection. Thus, the spread will slow after the easy routes have been exploited.
- vkou 5y ago
  > Further, there was an argument way back, that the number infected but symptom-free was much higher than estimated. This argument was made many, many times over the past year and a half by people insisting that <their area has hit herd immunity and everything is fine and we can fully re-open>. Inevitably, like clockwork, the wave of COVID that would follow would dwarf the previous one. The only thing that has broken this pattern has been mass vaccinations. It seems that high rate of antibody sero-prevalence in the population only protects you from COVID on paper.
  - reducesuffering 5y ago
    See North and South Dakota, who after initially receiving a first huge wave before there were vaccines, never encountered any significant second wave. They are the best candidates I've seen for a possible herd immunity all the way back to December. https://www.worldometers.info/coronavirus/usa/north-dakota/ https://www.worldometers.info/coronavirus/usa/north-dakota/ https://www.worldometers.info/coronavirus/usa/south-dakota/ https://www.worldometers.info/coronavirus/usa/south-dakota/
    - owenversteeg 5y ago
      Interesting! That does look promising. South Dakota has 762k people and 125k positive tests. The CDC assumes that 1 in 4.2 infections were reported, so that would be 525k people infected total. 52.8% of people got vaccinated. Assuming there's no correlation between getting vaccinated and getting infected (which I'd assume isn't 100% correct), you can assume that of the 295k uninfected, 156k got vaccinated. So that'd be a total of 525k infected+156k vaccinated and not infected = 681k = 89.4% immunity.
shanecleveland 5y ago
>> It may also be the case that those inclined to be skeptical of vaccines were also the ones who exposed themselves to infection most during the pandemic, through disdain for social distancing, mask-wearing, etc. I anecdotally am finding this to be the case
NoPicklez 5y ago
Australia definitely doesn't have or has ever had herd immunity and our total cases since the beginning are only 30k. Which represents only 0.12% of our countries population. We've faced strict lockdowns and limited access to vaccines to which makes us a ticking time bomb if we were to let current cases go rampant.
bartimus 5y ago
You can deduce the number of required infections by taking an IFR and the given total deaths of 613000. IFR: 0.15 = 613000 * 1 / 0.0015 = 408 million infections (124% population) IFR: 0.3 = 613000 * 1 / 0.003 = 204 million infections (62% population) IFR: 0.6 = 613000 * 1 / 0.006 = 102 million infections (31% population) So in case of the lower IFR would implicate there must be many reinfections. And those reinfections are still deadly. It would imply immunity isn't long-lasting. So best to keep routinely boosting your immunity through vaccines. This would probably be the least favorable scenario. In the case of the higher IFR would implicate there's still some herd immunity to go. It also implicates infections are more deadly. So better boost herd immunity by getting the vaccine. This would actually be the more favorable scenario if we're going to be able to beat Covid.

by arbuge 5y ago

billiam 5y ago

I don't know what the point of such conjecture is. Of course we don't know how much immunity comes from infection, and it is quite clear from the spread of delta that we are nowhere near herd immunity in the developed world, even in places like Israel. I had a coronavirus called a cold last year; does that mean I'm immune this year? Unlikely in the long term with COVID. The entire concept of herd immunity may be a mirage: if the (rare) breakthrough infections in vaccinated people like me spread just as much virus as unvaccinated, then there may be a huge potential for incubating new strains among the mRNA-ed that may elude all our current vaccines. And unlike a lot of viruses, the latest variants may be just as lethal as the earlier ones. Usually viruses become more transmissible and less lethal in response to rational behavior in their hosts--but humans are proving we're not rational.

infamouscow 5y ago
You're missing the point because the media (and their pharmaceutical advertisers) have framed everything in terms of vaccination, as if the human immune system is incapable of surviving COVID and it's variants. All viruses get less lethal as time goes on, not stronger, despite all the fear porn that has been indoctrinated into the public over the last year and a half.
- anthonyu 5y ago
  Certain viruses maintained their lethality as time went on. Smallpox was very lethal throughout time. Influenza lethality ebbs throughout history. I don't think we can or should depend on less-lethal, common-cold-like symptoms from Covid-19 at any point.
  - rajin444 5y ago
    Is there a reason we shouldn't expect it to behave like most coroanviruses?
    - cortic 5y ago
      There actually is. The evolutionary selection pressure on most coronaviruses exists throughout its infectious stage. So in order to be more infectious for longer the coronavirus would become less symptomatic and so less serious. But with C19 we are aggressively isolating people with symptoms. This focuses evolutionary selection pressure on the initial infectious stage. In order to be more infectious the virus increases viral load and shedding, causing more serious symptoms; which would be an evolutionary disadvantage, except isolation renders this disadvantage moot. Also natural immunity general focuses on the nucleus of the virus, vaccine immunity is to the spike. So this forces mutations in different proteins, which has different results.
      - vimy 5y ago
        Are you saying without lockdowns it would have turned in a regular cold by now?
        deleted 5y ago
        [deleted]
        cortic 5y ago
        Not lock-downs specifically. Testing and isolating, Maybe, but it would have cost many more lives.
rajin444 5y ago
> Usually viruses become more transmissible and less lethal in response to rational behavior in their hosts--but humans are proving we're not rational. I was under the impression viruses became less lethal because if they became more, they'd kill off their hosts and be less likely to spread. There's a chance you get some super virus that becomes both more transmissible and lethal, but that is very rare (from what I can see).
- AbortedLaunch 5y ago
  It depends. It’s hard to model and even think about the selection pressures accurately. West Nile virus showed a marked increase in virulence in corvids recently as did rabbit hemorrhagic disease. And let’s not forget about Mareks disease, where a non-sterilizing vaccine is thought to have contributed to a massive increase in virulence, killing nearly 100% of unvaccinated chickens now vs causing mild disease decades ago.
- CraigJPerry 5y ago
  Does that not assume that you’re symptomatic at the same time you’re spreading the virus? With covid you appear to be able to spread before you know you have it. Given that, what force would cause the virus to be selected for less lethality? With a different presentation of disease where symptoms and spread occur concurrently then there would be a pressure on the virus selecting for strains that arent so lethal a carrier has no chance to spread. In covid’s case, that pressure doesn’t exist as far as i can see?
- outworlder 5y ago
  > I was under the impression viruses became less lethal because if they became more, they'd kill off their hosts and be less likely to spread. Only if the lethality is negatively impacting their fitness. If it can spread to another host quickly, who cares if the previous host dies. There's no selective pressure against it. Which is why Delta is scary. Not just because of the higher viral load, but new strains could be more lethal and still not be selected against.
- deleted 5y ago
  [deleted]
notJim 5y ago
> Of course we don't know how much immunity comes from infection Come on, this is silly. We haven't learned nothing over the last year. https://www.nih.gov/news-events/nih-research-matters/lasting-immunity-found-after-recovery-covid-19 https://www.nih.gov/news-events/nih-research-matters/lasting...
- BeefWellington 5y ago
  This is true, however those studies are for the initial SARS-COV-2 strain and doesn't make any mention of the variants. It's also worth noting that's a study of ~200 people. Given then times we're in it's an excellent sign and possible reason for cautious optimism and I'm sure a larger scale study is much harder to pull off in the midst of the pandemic. That said, I have yet to see a study on the rate of reinfection of any of the variants against people who had already been infected with the initial strain, and how well that is survived, etc.
throwaway8582 5y ago
> I had a coronavirus called a cold last year; does that mean I'm immune this year? There are supposedly over 200 different viruses that can cause the common cold (https://www.nih.gov/news-events/nih-research-matters/understanding-common-cold-virus https://www.nih.gov/news-events/nih-research-matters/underst...). So it's quite possible for immunity to any individual strain to last a very long time and still get multiple colds per year. > Usually viruses become more transmissible and less lethal in response to rational behavior in their hosts--but humans are proving we're not rational. Our own "rationality" doesn't matter much, if a virus leaves you bed-ridden or dead, that makes it very hard for you spread it regardless of your choices. The fact that we have so many different viruses which essentially cause more or less the same "common cold" proves that there is very strong evolutionary pressure for a virus to behave this way.

ikawe 5y ago

> and it may also be the case that those who have a tendency to be skeptical of vaccines also were the ones most out and about and exposing themselves during the pandemic, i.e. the ones with the highest chance of being infected. Sure, _maybe_. > [...] would seem to indicate that most Western populations are already at herd imnmunity by this point Given that infections are still rising pretty hard, what indicates to you that we are _at_ this point, and not, say, 6 months out?

basch 5y ago

Not as sensationally reported is that, fatality rate (the proportion of people who die of those who tested positive) appears to be falling slightly, and is at its lowest in 2+ months. https://www.mayoclinic.org/coronavirus-covid-19/map https://www.mayoclinic.org/coronavirus-covid-19/map

zwily 5y ago
This would most likely be due to the vaccines, no?
genericuser314 5y ago
I think that's because of different vaccine uptake by age cohort. People 65+ have always been most likely to require intervention and they are also the most vaccinated age cohort - ~80% vaccinated in the US. [0] [0]: https://www.mayoclinic.org/coronavirus-covid-19/vaccine-tracker https://www.mayoclinic.org/coronavirus-covid-19/vaccine-trac...

felipellrocha 5y ago

> Left out in the discussion seem to be the unvaccinated but already infected. As far as I know, prior infection confers at least some degree of immunity. We don't know how much, though. There are cases in which vaccine performs better than a natural infection, there are cases in which the vaccine performs worse than natural infection. Without time for a study, it's impossible to know where we lie with Covid.

gpt5 5y ago
It's not impossible to estimate for COVID. Re-infections in COVID are exceedingly rare.
- fortuna86 5y ago
  There's no way of knowing this, considering the amount of asymptomatic cases that are never tested or recorded.
  - deleted 5y ago
    [deleted]
  - nradov 5y ago
    The UK is running human challenge trials to determine that. https://www.reuters.com/world/uk/new-uk-challenge-trial-studies-if-people-can-catch-coronavirus-again-2021-04-18/ https://www.reuters.com/world/uk/new-uk-challenge-trial-stud...
    - fortuna86 5y ago
      It's not if https://www.fox10tv.com/news/coronavirus/getting-covid-19-twice-alabama-health-officials-seeing-more-re-infections/article_21d4404e-effd-11eb-acde-a7bd20cc64d3.html https://www.fox10tv.com/news/coronavirus/getting-covid-19-tw... https://www.nbclosangeles.com/on-air/one-mans-experience-about-getting-covid-twice-even-after-getting-vaccinated/2642507/ https://www.nbclosangeles.com/on-air/one-mans-experience-abo... https://www.sciencemag.org/news/2020/11/more-people-are-getting-covid-19-twice-suggesting-immunity-wanes-quickly-some https://www.sciencemag.org/news/2020/11/more-people-are-gett... But how often and what are the consequences.

bawolff 5y ago

> Adding those two populations together would seem to indicate that most Western populations are already at herd immunity by this point That's assuming that nobody who got covid later got vaccinated (or got it before the vaccine kicked in). That seems like a very unrealistic assumption to me. On the other side, there are probably a lot more cases than are reported. You're right that it almost certainly matters for heard immunity, but i think you need a much more complex model to know how much of an effect it has.

throw_nbvc1234 5y ago
https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burden.html https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burd... CDC estimated that 1/4 covid infections had an associated positive test. I did the same kind of napkin math you're referring too for Floridia a few months back and they'd could have been at 80% of the population with some level of immunity. But napkin math probably isn't a good way to run a pandemic response. Just like herd immunity doesn't really matter at an individual level.
- bawolff 5y ago
  I'm also not sure how much the usa experience applies to other countries. They seem to have not liked lockdowns and masks very much.

stefan_ 5y ago

This is an exposition on Dunning Kruger. What is it going to be, herd immunity or surges? Can't be both.

nostrademons 5y ago

The herd immunity threshold changed with Delta, which I've heard has an R0 of 8-10 (compare 3.5-4.5 for the UK Alpha variant, and about 2.5 for the original strain). Instead of 60% vaccination, you'd need 90%, and will likely overshoot that. It wouldn't surprise me if the UK's cases are now dropping because they reached that threshold, but I doubt the US is there now. Probably Delta will blow through literally all the remaining unvaccinated people and that'll be the last surge, at least unless we get a vaccine-resistant strain.

deleted 5y ago
[deleted]
mensetmanusman 5y ago
“ Instead of 60% vaccination, you'd need 90%, and will likely overshoot that.” 60% (Vaccinated + Previously Infected)
- crowbahr 5y ago
  Delta variant can reinfect.
  - arwhatever 5y ago
    It's not a binary consideration, but you have expressed it as such.
samizdat311 5y ago
These are very good points. I'd add that herd immunity isn't a clearly defined threshold, either. It's the point at which the effective R in a population is < 1 -- AKA exponential decay. With a circulating virus, depending on how much below 1 you get, exponential decay might take a few months or even a few years to get down to elimination. The current dip in the UK is trending toward the former. But it's further complicated by the fact that levels of immunity in the population will continue to oscillate up and down. (Nevermind that once schools open in September, 20% of the population with relatively sparse vaccination will be mixing in large cohorts). Another factor in herd immunity is vaccine efficacy - which is somewhere between 86% and 95% for the mRNA vaccines (and will continue to change). A herd immunity threshold of 90% presupposes a vaccine with 100% efficacy - when your vaccines are not that effective (not to mention, losing effectiveness over time) it bumps the threshold even higher. Right now, much of the population has some level of "sterilising immunity" from the first round of vaccines and previous infection (i.e. having enough circulating antibodies to potentially block symptomatic infection and transmission). But everything we know about existing respiratory viruses (and indications so far this year) suggest antibodies will wane. Of course, indications are most people will come away with robust cell-based immunity. (Those plucky T-cells and B-cells). But eradication for the UK looks *very* close to impossible given the near-total-abandonment of public health measures recently.

svara 5y ago

Interestingly, you can get multiple-wave dynamics even when very far from population-level herd immunity, and even without taking into account changes in behavior (for example, [1]). That's because of stochasticity in the process due to the fact that (1) most people infect no one, but some people infect many ("overdispersion") and (2) the population is not well mixed. In practice, of course, people respond to news about Covid waves and that contributes to the wave-like dynamics. Furthermore, new variants of the virus will be able to reach people that were "cautious enough" for a previous variant. That alone would also give you wave-like dynamics, basically every new variant would affect increasingly harder to reach people. Anyway, the point is, seeing these waves is super natural and expected and we can't deduce anything about population-level immunity from them without looking really really closely. [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526984/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526984/

hyperpallium2 5y ago

Further, there was an argument way back, that the number infected but symptom-free was much higher than estimated. This would be enhanced by a hypothesised variant, that is more contagious, but less harmful - it would theoretically dominate, because its spread would be unimpeded. I don't know if these arguments have been tested; nor how to test them. Separately, the physical social graph is not uniform, but complex. There can easily be narrower channels that have a lower probability of conducting infection. Thus, the spread will slow after the easy routes have been exploited.

vkou 5y ago
> Further, there was an argument way back, that the number infected but symptom-free was much higher than estimated. This argument was made many, many times over the past year and a half by people insisting that <their area has hit herd immunity and everything is fine and we can fully re-open>. Inevitably, like clockwork, the wave of COVID that would follow would dwarf the previous one. The only thing that has broken this pattern has been mass vaccinations. It seems that high rate of antibody sero-prevalence in the population only protects you from COVID on paper.
- reducesuffering 5y ago
  See North and South Dakota, who after initially receiving a first huge wave before there were vaccines, never encountered any significant second wave. They are the best candidates I've seen for a possible herd immunity all the way back to December. https://www.worldometers.info/coronavirus/usa/north-dakota/ https://www.worldometers.info/coronavirus/usa/north-dakota/ https://www.worldometers.info/coronavirus/usa/south-dakota/ https://www.worldometers.info/coronavirus/usa/south-dakota/
  - owenversteeg 5y ago
    Interesting! That does look promising. South Dakota has 762k people and 125k positive tests. The CDC assumes that 1 in 4.2 infections were reported, so that would be 525k people infected total. 52.8% of people got vaccinated. Assuming there's no correlation between getting vaccinated and getting infected (which I'd assume isn't 100% correct), you can assume that of the 295k uninfected, 156k got vaccinated. So that'd be a total of 525k infected+156k vaccinated and not infected = 681k = 89.4% immunity.

shanecleveland 5y ago

>> It may also be the case that those inclined to be skeptical of vaccines were also the ones who exposed themselves to infection most during the pandemic, through disdain for social distancing, mask-wearing, etc. I anecdotally am finding this to be the case

NoPicklez 5y ago

Australia definitely doesn't have or has ever had herd immunity and our total cases since the beginning are only 30k. Which represents only 0.12% of our countries population. We've faced strict lockdowns and limited access to vaccines to which makes us a ticking time bomb if we were to let current cases go rampant.

bartimus 5y ago

You can deduce the number of required infections by taking an IFR and the given total deaths of 613000. IFR: 0.15 = 613000 * 1 / 0.0015 = 408 million infections (124% population) IFR: 0.3 = 613000 * 1 / 0.003 = 204 million infections (62% population) IFR: 0.6 = 613000 * 1 / 0.006 = 102 million infections (31% population) So in case of the lower IFR would implicate there must be many reinfections. And those reinfections are still deadly. It would imply immunity isn't long-lasting. So best to keep routinely boosting your immunity through vaccines. This would probably be the least favorable scenario. In the case of the higher IFR would implicate there's still some herd immunity to go. It also implicates infections are more deadly. So better boost herd immunity by getting the vaccine. This would actually be the more favorable scenario if we're going to be able to beat Covid.